The present invention relates to a portable devices and more particularly to a low cost power distribution system and method for a portable device that is powered by a recharger unit or alternatively a rechargeable battery. The portable device includes a bridge battery for powering the portable device in the event the rechargeable battery is removed.
Portable electronic devices (e.g. notebook computers, cellular telephone, cordless telephones mobile data terminals, radio frequency portable communication devices, etc.) typically include a rechargeable battery that is charged by a recharging unit plugged into an AC power source, such as that found in conventional 115 VAC lines. The recharging unit powers the portable device, while simultaneously charging the rechargeable battery. The portable device switches over to battery power upon removal of the portable device from the charging unit or the power source. Most intelligent portable devices employ a bridge battery that is utilized during the removable of the main rechargeable battery when it powers the portable device. The main function of the bridge battery is to insure that data stored in a Random Access Memory (RAM) device is not lost during swapping of the rechargeable battery. The bridge battery is usually a much smaller battery because during a battery swap, the portable device normally will enter a low current or suspend mode, so that most current drawn from the bridge battery is used to refresh the RAM device, until a new main battery is installed into the device.
Many portable devices employ complicated switching or logic circuitry when changing from the rechargeable device power to the main battery power, and from the main battery power to the bridge battery power. The switching or logic circuitry takes up valuable space on a circuit board that could be utilized to perform the function of the portable device. In some cases, additional circuit boards are necessary to house the switching or logic circuitry. This increases the size and cost of the portable device. Furthermore, some of these portable devices employ expensive power management and supervisory circuitry to cause the functional components in the portable device to enter different modes, depending on the type of unit powering the portable device or the current status of the unit powering the portable device. The additional power management and supervisory circuitry adds to the size, the cost and also to the complexity of the portable device.
Accordingly, there is a strong need in the art for a system and/or method that can provide power distribution for a portable electronic device at low cost, while reducing space utilized in employing such a system.
According to a preferred embodiment of the present invention, a power distribution system is provided for distributing power in a portable device being coupleable to a charging system and including a main battery power system and a bridge battery power system. The charge system is coupled to a power bus through a diode. The main battery power system and the bridge battery system are also both coupled to the power bus through diodes. A predetermined voltage level is set with respect to the charging system, the main battery and the bridge battery such that if all three are coupled to the bus, the recharging system both powers the unit and recharges the main battery. If the recharging system is removed, the main battery power system powers the portable device, and if the main battery power system is removed, the bridge battery will provide power to the portable device. The distribution system also includes a monitoring system for measuring a predetermined charge level on the battery and disabling a FET switch, so that the main battery stops charging to protect the main battery against overcharging. A monitoring system is also provided for monitoring the voltage level of the main battery utilizing a comparator system. Accordingly, the present invention provides for a very low cost power distribution system for portable devices.
Thus, according to one aspect of the present invention, a power distribution system is provided that provides power to functional and power circuitry on a portable device. The system includes a main battery system coupled to a power bus through a first switch system and a charging system coupled to the power bus through a second switch system. The charging system provides power to the power bus through the second switch system while the charging system is coupled to the second switch system and the main battery system provides power to the power bus through the first switch system upon removal of the charging system.
In accordance with another aspect of the present invention a power distribution system is provided that provides power to functional and power circuitry on a portable device. The system includes a main battery system coupled to a power bus through a main battery diode and a bridge battery system coupled to the power bus through a bridge battery diode. The voltage level of the bridge battery is lower than the voltage level of the main battery and removal of the main battery system causes the second switch system to allow the bridge battery system to provide power to the power bus.
In accordance with yet another aspect of the present invention, a method is provided for power distribution in a portable device including a power bus coupled to a device power and functional circuitry. The method includes the steps of providing a main battery system coupled to a power bus through a main battery diode, providing a charging system coupled to the power bus through a charger diode and providing a bridge battery system coupled to the power bus through a bridge battery diode wherein the charging system has a voltage level above the main battery voltage level and the main battery has a voltage level above the bridge battery, such that the charger powers the power bus if the charger is present, the main battery powers the power bus if the charger is not present and the bridge battery powers the bus if the charger and the main battery are not present.
In accordance with another aspect of the present invention, a power distribution system is provided that provides power to functional and power circuitry on a portable device. The system includes means for providing main battery power. The means for providing main battery power includes means for coupling the means for providing main battery power to a power bus. The system also includes means for recharging the means for providing main battery power. The means for recharging the means for providing main battery power includes means for coupling the means for recharging to the power bus. The means for charging having a voltage level that is at a predetermined level above a voltage level of the means for providing main battery power causing the means for charging to simultaneously provide power to the power bus and recharge the means for providing main battery power.
In accordance with yet another aspect of the present invention, a power distribution system for providing power to functional and power circuitry on a portable device is provided. The system includes a main battery system coupled to a power bus through a main battery diode, a charging system coupled to the power bus through a charger diode and a bridge battery system coupled to the power bus through a bridge battery diode. The charging system has a voltage level that is at a predetermined level above a voltage level of the main battery system and the voltage level of the bridge battery system is lower than the voltage level of the main battery system. If the charging system is present, the charger diode is forward biased and the charging system provides power to the power bus. If the charging system is not present, the main battery diode becomes forward biased and the main battery system provides power to the power bus. If the charging system and the main battery system are not present, the bridge battery diode becomes forward biased and the bridge battery system provides power to the power bus.
To the accomplishment of the foregoing and related ends, the invention then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such embodiments and their equivalents. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.